Recently bought a house that's about 40 years old. The previous owner was clearly very fond of doing the wiring himself and has left me some idiosyncrasies to work out. One is this box in one of my bedrooms. No idea what it is, or is supposed to do but I see extra wires coming straight out of the sheet rock on the bottom of it. Can anyone tell me what it is?generic DC adapter plugged into electrical socket.

3 Answers 3


Conveniently, it still had the UPC barcode label and you captured it quite clearly in the picture.

A search at upcdatabase.com shows that it is:

Description     Brinks Home Security System AC Power Adaptor
Size/Weight     5x3x3, 12 ounces 
Issuing Country United States

A Google Search for that UPC brings up a number of hits, including on at Parts Express that shows the following specs:

Universal UB1640W 16.5 VAC 40 VA Plug-In Wall Transformer

AC Output Voltage   16.5 V
Current Capacity    2400 mA
Center/Tip Polarity AC Plug 
Input Voltage       110~120 VAC

generic DC adapter showing outlet prongs and wire connection screws.

So, it appears to be a low voltage 16.5 VAC transformer that is (or at least was) a part of a home security system. Looks like the screw on top is meant to screw into the outlet for semi-permanent installation.

Of course, it's possible that it was re-purposed for something else like low voltage lighting, a doorbell, or who knows what it may be used for.

  • 9
    This. Simply put, it is a transformer to power an alarm system. Oct 22, 2015 at 10:55
  • 2
    Well played, sir! Oct 22, 2015 at 14:36
  • 1
    I bought a house built in the 1990's (in the USA). It had a few of these that were put in place by a security alarm company. One powered the alarm control panel. The other powered a motion sensor up in one corner of a room. Seemed kinda hokey, but it was a system installed by a large, nationally known security company...
    – bitsmack
    Oct 22, 2015 at 16:11
  • 3
    @Joe - also the poster's observation I see extra wires coming straight out of the sheet rock on the bottom of it also indicates wires coming through the sheetrock.
    – Johnny
    Oct 22, 2015 at 20:48
  • 4
    Well, yes, if you read the entire post, but who does that?
    – Joe
    Oct 22, 2015 at 20:49

A transformer to reduce the house current to low voltage, to power something.

It can be for any number of things. If it goes into the wall, check the other side, there is a chance the wire comes straight through.


This is a transformer or DC power supply. Odds are that this was installed years ago by the telephone company to power land-line telephones with light-up dials ("princess" phones). This was well before LED lighting that pulled small-enough power to run right off of the power from the central office.

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